Kde plasma does not remember the location of desktop icons

It works. If it doesn’t work then check if you have UNSORTED selected under the menu options when you right click. Also maybe it is possible your config files have wrong/unsupported values and a reset could fix weird issues, or maybe just playing with all settings back and forth could sort things out, but it definitely work for me since long time now. It can change the items position on specific conditions like changing desktop resolution, switching main monitor when having multiple, things like that.